This invention relates to a wireless modem.
Computers typically connect to networks, such as the Internet, through a xe2x80x9cwiredxe2x80x9d device, such as a modem. Wired, in this context, refers to wired connections, such as telephone lines, Ethernet cable, and the like.
There are limitations associated with the use of wired devices. For example, wired devices have limited portability. Also, since wired devices require a nearby telephone jack or outlet, their installation options are limited. Wireless modems have been developed to reduce the need for wired computer connections.
In general, in one aspect, the invention is directed to modem circuitry for establishing a communication link between a computer and a device that receives a modulated analog data signal over a wireless link. The modem circuitry includes a coder/decoder for generating a digitized signal based on the modulated analog data signal, and a processor for demodulating the digitized signal to produce a digital data output signal.
This aspect of the invention may include one or more of the following. A three-conductor interface couples the coder/decoder to the device. The modulated analog data signal is transmitted from the device, over the three-conductor interface, to the coder/decoder. The device is a wireless telephone and the three-conductor interface is a headset interface on the wireless telephone.
The modulated analog data signal uses QAM modulation. The modulated analog data signal has substantially no nonlinear distortion and the processor performs echo canceling on the digitized signal. The modulated analog data signal is transmitted over RF using digital frequency modulation or analog frequency modulation.
In general, in another aspect, the invention is directed to a modem for transmitting data between a computer and a telephone line. This aspect of the invention features a base unit which receives a data signal from the telephone line and transmits the data signal over a wireless link. A device receives the data signal over the wireless link and outputs an analog data signal that corresponds to the data signal. A modem card receives the analog data signal from the device, digitizes the analog data signal to produce a digital signal, demodulates the digital signal, and provides an output digital data signal to the computer.
This aspect of the invention may include one or more of the following features. The modem card receives a digital signal data from the computer, generates a digitized analog signal, converts the digitized analog signal to an analog data signal, and outputs the analog data signal to the device. The device receives the analog data signal and outputs an RF signal that corresponds to the analog data signal to the base unit over a wireless link. The base unit receives the RF signal over the wireless link and outputs a data signal that corresponds to the RF signal over the telephone line. A three-conductor cable connects the modem card to the device and the modem card receives the analog data signal from the device over the three-conductor cable.
The device is a wireless telephone that is dialed manually to establish a data link between the computer and the telephone line. The base unit includes circuitry that limits an amount of nonlinear distortion in the data signal. The modem card includes circuitry that performs an echo canceling routine on the digital signal. The circuitry in the base unit includes an automatic gain controller and the circuitry in the modem card includes a processor. The echo canceling routine performed by the modem card is a linear echo canceling routine.
The base unit and the device run error detection routines to detect errors in the data signal. When an error is detected, the base unit and the device switch to a clear frequency channel, over which the data signal is transmitted. The error detection routines use a parity bit to check for errors in the data signal.
The device may be a cordless telephone handset and the base unit may be a cordless telephone base unit. Alternatively, the device may be a cellular telephone and the base unit may be a cellular base station.
In general, in another aspect, the invention is directed to a method of transmitting data from a telephone line to a computer using a modem card connected to a wireless telephone handset. The wireless telephone handset communicates with the telephone line via a base unit. The method includes establishing a connection from the computer to the telephone line via the modem card, the telephone handset, and the base unit; receiving a data signal from the telephone line at the base unit; and transmitting the data signal from the base unit to the wireless telephone handset over a wireless link. The method also includes transmitting an RF modulated voiceband data signal that corresponds to the data signal from the telephone handset to the modem; and receiving the voiceband data signal at the modem, digitizing and demodulating the voiceband data signal, and outputting a digital data signal to the computer.
Other features and advantages of the invention will become apparent from the following description, including the claims and drawings.